1. Field of the Invention
The present invention relates to the production of aryl ketones by the reaction of aromatic hydrocarbon compounds and aromatic or aliphatic acyl halides in the presence of anhydrous iron (III) chloride. In particular, the invention relates to reaction under conditions of elevated temperature and pressure. The invention specifically relates to the synthesis of benzophenone, methylbenzophenone and dimethylbenzophenone.
2. Information Disclosure Statement
Aryl ketones such as benzophenone are important organic reagents used as fixatives for heavy perfumes and soaps and are used in the manufacture of a variety of pharmaceuticals, industrial chemicals and insecticides.
The usual method of synthesis of aryl ketones involves the reaction of an aromatic hydrocarbon or halogenated aromatic hydrocarbon with an aromatic or aliphatic acyl halide in the presence of stoichiometric amounts of AlCl.sub.3. The product of this reaction is an aluminum chloride derivative of the aryl ketone that must be hydrolyzed to provide the final ketone product. This reaction scheme has a number of inherent economic and practical disadvantages, including the need for the final hydrolysis step; the consumption in the reaction of stoichiometric amounts of AlCl.sub.3 ; the production of a large amount of aluminum chloride residue from the reaction that must be recycled or discarded; and the production of large quantities of waste water contaminated with the aromatic hydrocarbon that must be treated and detoxified before disposal. The development of alternative methods of synthesis is desirable.
The use of iron (III) chloride as a catalyst for the synthesis of aryl ketones has been described in the prior art.
Prill, U.S. Pat. No. 2,879,296 teaches the use of ferric chloride as a catalyst for the production of halogenated aromatic ketones from mixtures of halogenated aromatic hydrocarbons such as chlorobenzene and an acylating agent such as benzoyl chloride.
Prill and Kosmin, U.S. Pat. No. 2,879,297 teach the synthesis of diaryl ketones from aromatic carboxylic acid, aromatic compounds capable of acylation and aryltrichloromethane, the reaction catalyzed by Frieder-Crafts catalysts such as iron (III) chloride and AlCl.sub.3, as well as other catalysts such as metallic zinc.
Grard, U.S. Pat. No. 3,833,677 teaches the production of substituted and unsubstituted aromatic ketones from benzoyl halides and substituted or unsubstituted aromatic compounds such as benzene, catalyzed by metallic halides of the class consisting of ruthenium, osmium, rubidium and coordination complexes of such substances at temperatures from 50.degree.-300.degree. C.
Effenberger et al., U.S. Pat. No. 3,907,837 teach the preparation of aromatic ketones by reaction of aromatic compounds with acyl chlorides or acyl anhydrides in the presence of catalytic amounts of aromatic polynitrosulfonic acid. These inventors describe the synthesis of benzophenone from mixtures of benzene and benzoyl chloride at 160.degree. C. and superatmospheric pressure using trinitrobenzenesulfonic acid as a catalyst.
Schaffner et al., U.S. Pat. No. 3,933,917 relates to the production of anthraquinone-1-carboxylic acid via a reaction pathway that features dimethylbenzophenone as an intermediate.
Taylor, U.S. Pat. No. 4,025,580 teaches the modification of styrene and polystyrene and derivatives by acylation using aromatic acid chlorides such as benzoyl chloride and catalysts such as iron (III) chloride.
Gors et al., U.S. Pat. No. 4,814,508 relates to the production of aromatic ketones using a mixture of a Lewis acid such as iron (III) chloride and a Lewis base such as an organic amide in an aprotic solvent such as methylene chloride.
The use of elevated temperature and/or pressure for the synthesis of aryl ketones has been described in the prior art.
Schmerling and Ipatieff, U.S. Pat. No. 2,386,007 relates to the production of alkyl and aryl ketones from aromatic hydrocarbons and alkyl or aryl acid chlorides using ZnCl.sub.2 as a catalyst. The synthetic reaction proceeds at pressures of up to 200 atmospheres (atms) and temperatures of 100.degree.-350.degree. C.
Sachanen and Caesar, U.S. Pat. No. 2,528,789 teach the synthesis of benzophenone from benzene and benzoyl chloride using temperatures of 300.degree.-700.degree. C. and pressures of 1750-2500 lb/in.sup.2 (psi; 119-170 atms) in the absence of a catalyst.
Schmerling, U.S. Pat. No. 3,883,594 relates to the production of aromatic ketones and alkylated derivatives thereof by reaction between an aromatic hydrocarbon and an acyl halide in the presence of a Friedel-Crafts catalyst and a saturated hydrocarbon containing at least one tertiary carbon atom.
Desbois, U.S. Pat. No. 4,453,012 relates to the synthesis of phenylketones from halo- or trihalomethylbenzenes in the presence of hydrofluoric acid and boron trifluoride under a pressure exceeding 1 atm.
Desbois, U.S. Pat. No. 4,454,350 relates to the acylation of halo- or trihalomethylbenzene by reaction with a carboxylic acid in the presence of hydrofluoric acid and boron trifluoride under a pressure exceeding 1 atm.
Desbois, U.S. Pat. No. 4,618,726 relates to the synthesis of benzophenone from derivatives of benzene substituted with deactivating groups and phosgene in the presence of hydrofluoric acid and boron trifluoride.
Baker et al., U.S. Pat. No. 4,922,026 provides for the acylation of benzene, toluene or anisole using difunctional acyl halides or anhydrides of organic acids and catalytic amounts of iron (III) chloride at temperatures of 50.degree.-300.degree. C. and pressures of 10-1000 psi (0.7-70 atm). The preferred acylating agent is isophthaloyl chloride.
Engel, U.S. Pat. No. 4,251,675 teaches the synthesis of diphenylmethane from benzene and benzyl chloride in the presence of FeCl.sub.2 catalyst.
Pearson and Buehler, Synthesis (October 1972) 533-542 disclose Friedel-Crafts acylation using little or no catalyst in a reaction performed at elevated temperatures and atmospheric pressure.
The prior art thus contains numerous attempts to develop efficient and economically advantageous methods of aryl ketone synthesis. The present invention relates to the use of anhydrous iron (III) chloride in catalytic amounts for the production of aryl ketones from aromatic hydrocarbon compounds and aromatic or aliphatic acyl halides under conditions of elevated temperature and pressure. The teachings of the present invention describe a novel and unexpected combination of temperature, pressure and an amount of anhydrous iron (III) chloride that efficiently and economically produces high yields of aryl ketones. While the related art teaches the synthesis of benzophenone from benzene and benzoyl chloride, the use of anhydrous iron (III) chloride in the synthesis of benzophenone, and the use of conditions of elevated temperature and pressure for benzophenone synthesis, it neither teaches nor suggests the combination of the use of catalytic amounts of FeCl.sub.3 under conditions of elevated temperature and pressure for the synthesis of benzophenone as described in the present invention.